Probably much covered but a fresh issue for me:-)

Viessman modulating system boiler. Reasonably well insulated house.

Underfloor heating controlled by 10 (yes 10) thermostats and DHW given
priority.

In the excitement of moving house, I hadn't given much thought to time
clock settings and left 24 hour operation selected. With the relatively
warm Winter weather I have realised that the boiler spends most of the
burn time on the lowest of the 5 available settings.

Does this matter? I can cheat by limiting the CH on periods to provide a
bigger load. Any thoughts?
--
Tim Lamb

On Sunday, 29 December 2019 13:01:26 UTC, Tim Lamb wrote:
Probably much covered but a fresh issue for me:-)

Viessman modulating system boiler. Reasonably well insulated house.

Underfloor heating controlled by 10 (yes 10) thermostats and DHW given
priority.

In the excitement of moving house, I hadn't given much thought to time
clock settings and left 24 hour operation selected. With the relatively
warm Winter weather I have realised that the boiler spends most of the
burn time on the lowest of the 5 available settings.

Does this matter? I can cheat by limiting the CH on periods to provide a
bigger load. Any thoughts?
--
Tim Lamb

A constant low burn will be more efficient than on-off-on-off.
If only by eliminating the post and pre burn "purges" of cold air through the boiler.

https://idealboilers.com/support/faq...fan-post-purge

https://www.gobdc.com/purging-airflo...tion-required/

On Sunday, 29 December 2019 13:01:26 UTC, Tim Lamb wrote:
Probably much covered but a fresh issue for me:-)

Viessman modulating system boiler. Reasonably well insulated house.

Underfloor heating controlled by 10 (yes 10) thermostats and DHW given
priority.

In the excitement of moving house, I hadn't given much thought to time
clock settings and left 24 hour operation selected. With the relatively
warm Winter weather I have realised that the boiler spends most of the
burn time on the lowest of the 5 available settings.

Does this matter? I can cheat by limiting the CH on periods to provide a
bigger load. Any thoughts?

Low burn is its most efficient mode.


NT

In message ,
writes
On Sunday, 29 December 2019 13:01:26 UTC, Tim Lamb wrote:
Probably much covered but a fresh issue for me:-)

Viessman modulating system boiler. Reasonably well insulated house.

Underfloor heating controlled by 10 (yes 10) thermostats and DHW given
priority.

In the excitement of moving house, I hadn't given much thought to time
clock settings and left 24 hour operation selected. With the relatively
warm Winter weather I have realised that the boiler spends most of the
burn time on the lowest of the 5 available settings.

Does this matter? I can cheat by limiting the CH on periods to provide a
bigger load. Any thoughts?

Low burn is its most efficient mode.

Yes but:-)

24 hours in low burn at X% or say 5 hours at Y% flat out.

--
Tim Lamb

On 29/12/2019 22:38:46, Tim Lamb wrote:
In message ,
writes
On Sunday, 29 December 2019 13:01:26 UTC, Tim LambÂ* wrote:
Probably much covered but a fresh issue for me:-)

Viessman modulating system boiler. Reasonably well insulated house.

Underfloor heating controlled by 10 (yes 10) thermostats and DHW given
priority.

In the excitement of moving house, I hadn't given much thought to time
clock settings and left 24 hour operation selected. With the relatively
warm Winter weather I have realised that the boiler spends most of the
burn time on the lowest of the 5 available settings.

Does this matter? I can cheat by limiting the CH on periods to provide a
bigger load. Any thoughts?

Low burn is its most efficient mode.

Yes but:-)

24 hours in low burn at X%Â* or say 5 hoursÂ* at Y% flat out.

Assuming the same excess O2 in flue gasses in each case and the same
flow return temperature, the former, as the heat exchanger will be more
efficient with the slower traversal of flue gasses.

That does depend on a good modulating burner.

On Sunday, 29 December 2019 22:42:41 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Sunday, 29 December 2019 13:01:26 UTC, Tim Lamb wrote:

Probably much covered but a fresh issue for me:-)

Viessman modulating system boiler. Reasonably well insulated house.

Underfloor heating controlled by 10 (yes 10) thermostats and DHW given
priority.

In the excitement of moving house, I hadn't given much thought to time
clock settings and left 24 hour operation selected. With the relatively
warm Winter weather I have realised that the boiler spends most of the
burn time on the lowest of the 5 available settings.

Does this matter? I can cheat by limiting the CH on periods to provide a
bigger load. Any thoughts?

Low burn is its most efficient mode.

Yes but:-)

24 hours in low burn at X% or say 5 hours at Y% flat out.

Sure, a house takes longer to heat up from cold. What point were you making?

In message ,
writes
On Sunday, 29 December 2019 22:42:41 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Sunday, 29 December 2019 13:01:26 UTC, Tim Lamb wrote:

Probably much covered but a fresh issue for me:-)

Viessman modulating system boiler. Reasonably well insulated house.

Underfloor heating controlled by 10 (yes 10) thermostats and DHW given
priority.

In the excitement of moving house, I hadn't given much thought to time
clock settings and left 24 hour operation selected. With the relatively
warm Winter weather I have realised that the boiler spends most of the
burn time on the lowest of the 5 available settings.

Does this matter? I can cheat by limiting the CH on periods to provide a
bigger load. Any thoughts?

Low burn is its most efficient mode.

Yes but:-)

24 hours in low burn at X% or say 5 hours at Y% flat out.

Sure, a house takes longer to heat up from cold. What point were you making?

From a total gas consumption POV I was wondering if running a boiler for
long periods at low output/high efficiency is better than drawing the
same total heat output but over a shorter period.

Off must use less gas:-) The house will be kept heated 24 hours anyway.

--
Tim Lamb

Low burn is its most efficient mode.


From a total gas consumption POV I was wondering if running a boiler
for long periods at low output/high efficiency is better than drawing
the same total heat output but over a shorter period.

Off must use less gas:-) The house will be kept heated 24 hours anyway.


Surely, that's what 'most efficient' means? I know nothing about boiler
efficiency. This is purely a semantic point.

Haven't seen any tripe from IMM for a while. This sort of thread used to attract him like a fly to a lump of ****.
Maybe someone killed him?

On Monday, 30 December 2019 09:27:45 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Sunday, 29 December 2019 22:42:41 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Sunday, 29 December 2019 13:01:26 UTC, Tim Lamb wrote:

Probably much covered but a fresh issue for me:-)

Viessman modulating system boiler. Reasonably well insulated house.

Underfloor heating controlled by 10 (yes 10) thermostats and DHW given
priority.

In the excitement of moving house, I hadn't given much thought to time
clock settings and left 24 hour operation selected. With the relatively
warm Winter weather I have realised that the boiler spends most of the
burn time on the lowest of the 5 available settings.

Does this matter? I can cheat by limiting the CH on periods to provide a
bigger load. Any thoughts?

Low burn is its most efficient mode.

Yes but:-)

24 hours in low burn at X% or say 5 hours at Y% flat out.

Sure, a house takes longer to heat up from cold. What point were you making?

From a total gas consumption POV I was wondering if running a boiler for
long periods at low output/high efficiency is better than drawing the
same total heat output but over a shorter period.

sounds like someone isn't grasping efficiency

Off must use less gas:-) The house will be kept heated 24 hours anyway.

On Monday, 30 December 2019 11:04:02 UTC, GB wrote:

Low burn is its most efficient mode.


From a total gas consumption POV I was wondering if running a boiler
for long periods at low output/high efficiency is better than drawing
the same total heat output but over a shorter period.

Off must use less gas:-) The house will be kept heated 24 hours anyway.


Surely, that's what 'most efficient' means? I know nothing about boiler
efficiency. This is purely a semantic point.

Efficiency is useful power out over power in.


NT

In message ,
writes
On Monday, 30 December 2019 09:27:45 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Sunday, 29 December 2019 22:42:41 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Sunday, 29 December 2019 13:01:26 UTC, Tim Lamb wrote:

Probably much covered but a fresh issue for me:-)

Viessman modulating system boiler. Reasonably well insulated house.

Underfloor heating controlled by 10 (yes 10) thermostats and DHW given
priority.

In the excitement of moving house, I hadn't given much thought to time
clock settings and left 24 hour operation selected. With the relatively
warm Winter weather I have realised that the boiler spends most of the
burn time on the lowest of the 5 available settings.

Does this matter? I can cheat by limiting the CH on periods to
provide a
bigger load. Any thoughts?

Low burn is its most efficient mode.

Yes but:-)

24 hours in low burn at X% or say 5 hours at Y% flat out.

Sure, a house takes longer to heat up from cold. What point were you making?

From a total gas consumption POV I was wondering if running a boiler for
long periods at low output/high efficiency is better than drawing the
same total heat output but over a shorter period.

sounds like someone isn't grasping efficiency

I'll happily try to understand an explanation. Maths was never a strong
point:-(

I assume boiler efficiency is non linear. Given that a fixed amount of
energy is required over a 24 hour period, and that boiler losses only
occur during firing, my uncertainty is whether a shorter firing period,
but at reduced efficiency, would use less gas overall.

This seems fundamental to matching boiler and set up to the expected
load.

Off must use less gas:-) The house will be kept heated 24 hours anyway.

--
Tim Lamb

On Tuesday, 31 December 2019 11:49:12 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Monday, 30 December 2019 09:27:45 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Sunday, 29 December 2019 22:42:41 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Sunday, 29 December 2019 13:01:26 UTC, Tim Lamb wrote:

Probably much covered but a fresh issue for me:-)

Viessman modulating system boiler. Reasonably well insulated house.

Underfloor heating controlled by 10 (yes 10) thermostats and DHW given
priority.

In the excitement of moving house, I hadn't given much thought to time
clock settings and left 24 hour operation selected. With the relatively
warm Winter weather I have realised that the boiler spends most of the
burn time on the lowest of the 5 available settings.

Does this matter? I can cheat by limiting the CH on periods to
provide a
bigger load. Any thoughts?

Low burn is its most efficient mode.

Yes but:-)

24 hours in low burn at X% or say 5 hours at Y% flat out.

Sure, a house takes longer to heat up from cold. What point were you making?

From a total gas consumption POV I was wondering if running a boiler for
long periods at low output/high efficiency is better than drawing the
same total heat output but over a shorter period.

sounds like someone isn't grasping efficiency

I'll happily try to understand an explanation. Maths was never a strong
point:-(

I assume boiler efficiency is non linear.

efficiency versus what is nonlinear?

Given that a fixed amount of
energy is required over a 24 hour period, and that boiler losses only
occur during firing, my uncertainty is whether a shorter firing period,
but at reduced efficiency, would use less gas overall.

If you need say 24kWh dumped into the house over the day, you could run the boiler (making up rounded guesstimated efficiency figures) thus:
1. 4kW output for 6hrs at 90% efficiency, thus consuming 24kWh/90% = 26.66kWh
2. 24kW out for 1hr at 80%, thus consuming 24/80% = 30kWh of gas.

In practice the efficiency difference is probably greater than that.
Losses when off are not zero but relatively trivial.


NT

This seems fundamental to matching boiler and set up to the expected
load.

Off must use less gas:-) The house will be kept heated 24 hours anyway.

In article ,
Tim Lamb wrote:
From a total gas consumption POV I was wondering if running a boiler for
long periods at low output/high efficiency is better than drawing the
same total heat output but over a shorter period.

sounds like someone isn't grasping efficiency

I'll happily try to understand an explanation. Maths was never a strong
point:-(

I assume boiler efficiency is non linear. Given that a fixed amount of
energy is required over a 24 hour period, and that boiler losses only
occur during firing, my uncertainty is whether a shorter firing period,
but at reduced efficiency, would use less gas overall.

This seems fundamental to matching boiler and set up to the expected
load.

Many seem to call something efficient if it simply works OK. And in that
respect an ancient boiler could be just as good as the best modern one.

True efficiency (for most) would be getting the same results for the
lowest running costs.

--
*Dancing is a perpendicular expression of a horizontal desire *

Dave Plowman London SW
To e-mail, change noise into sound.

In message ,
writes
On Tuesday, 31 December 2019 11:49:12 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Monday, 30 December 2019 09:27:45 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Sunday, 29 December 2019 22:42:41 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Sunday, 29 December 2019 13:01:26 UTC, Tim Lamb wrote:

Probably much covered but a fresh issue for me:-)

Viessman modulating system boiler. Reasonably well insulated house.

Underfloor heating controlled by 10 (yes 10) thermostats and

priority.

In the excitement of moving house, I hadn't given much
thought to time
clock settings and left 24 hour operation selected. With the

warm Winter weather I have realised that the boiler spends
most of the
burn time on the lowest of the 5 available settings.

Does this matter? I can cheat by limiting the CH on periods to
provide a
bigger load. Any thoughts?

Low burn is its most efficient mode.

Yes but:-)

24 hours in low burn at X% or say 5 hours at Y% flat out.

Sure, a house takes longer to heat up from cold. What point were
you making?

From a total gas consumption POV I was wondering if running a boiler for
long periods at low output/high efficiency is better than drawing the
same total heat output but over a shorter period.

sounds like someone isn't grasping efficiency

I'll happily try to understand an explanation. Maths was never a strong
point:-(

I assume boiler efficiency is non linear.

efficiency versus what is nonlinear?

Efficiency related to boiler output.

Given that a fixed amount of
energy is required over a 24 hour period, and that boiler losses only
occur during firing, my uncertainty is whether a shorter firing period,
but at reduced efficiency, would use less gas overall.

If you need say 24kWh dumped into the house over the day, you could run
the boiler (making up rounded guesstimated efficiency figures) thus:
1. 4kW output for 6hrs at 90% efficiency, thus consuming 24kWh/90% = 26.66kWh
2. 24kW out for 1hr at 80%, thus consuming 24/80% = 30kWh of gas.

In practice the efficiency difference is probably greater than that.
Losses when off are not zero but relatively trivial.

OK. Are such examples searchable for a particular boiler?

--
Tim Lamb

On Tuesday, 31 December 2019 14:22:06 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Tuesday, 31 December 2019 11:49:12 UTC, Tim Lamb wrote:

I assume boiler efficiency is non linear.

efficiency versus what is nonlinear?

Efficiency related to boiler output.

I expect it is.

Given that a fixed amount of
energy is required over a 24 hour period, and that boiler losses only
occur during firing, my uncertainty is whether a shorter firing period,
but at reduced efficiency, would use less gas overall.

If you need say 24kWh dumped into the house over the day, you could run
the boiler (making up rounded guesstimated efficiency figures) thus:
1. 4kW output for 6hrs at 90% efficiency, thus consuming 24kWh/90% = 26.66kWh
2. 24kW out for 1hr at 80%, thus consuming 24/80% = 30kWh of gas.

In practice the efficiency difference is probably greater than that.
Losses when off are not zero but relatively trivial.

OK. Are such examples searchable for a particular boiler?

I've not even looked. I suspect boiler mfrs probably just quote their best possible headline figure and say nowt else. Anyway efficiency is always going to decline as P_out increases for a given heat exchanger.


NT

On Tuesday, 31 December 2019 11:49:12 UTC, Tim Lamb wrote:
In message ,
writes
On Monday, 30 December 2019 09:27:45 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Sunday, 29 December 2019 22:42:41 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Sunday, 29 December 2019 13:01:26 UTC, Tim Lamb wrote:

Probably much covered but a fresh issue for me:-)

Viessman modulating system boiler. Reasonably well insulated house.

Underfloor heating controlled by 10 (yes 10) thermostats and DHW given
priority.

In the excitement of moving house, I hadn't given much thought to time
clock settings and left 24 hour operation selected. With the relatively
warm Winter weather I have realised that the boiler spends most of the
burn time on the lowest of the 5 available settings.

Does this matter? I can cheat by limiting the CH on periods to
provide a
bigger load. Any thoughts?

Low burn is its most efficient mode.

Yes but:-)

24 hours in low burn at X% or say 5 hours at Y% flat out.

Sure, a house takes longer to heat up from cold. What point were you making?

From a total gas consumption POV I was wondering if running a boiler for
long periods at low output/high efficiency is better than drawing the
same total heat output but over a shorter period.

sounds like someone isn't grasping efficiency

I'll happily try to understand an explanation. Maths was never a strong
point:-(

I assume boiler efficiency is non linear. Given that a fixed amount of
energy is required over a 24 hour period, and that boiler losses only
occur during firing, my uncertainty is whether a shorter firing period,

Boiler losses occur all the time the boiler is hotter than the ambient air.

There are several losses from boilers. All need taking into account.

On Tuesday, 31 December 2019 14:12:32 UTC, Dave Plowman (News) wrote:
In article ,
Tim Lamb wrote:
From a total gas consumption POV I was wondering if running a boiler for
long periods at low output/high efficiency is better than drawing the
same total heat output but over a shorter period.

sounds like someone isn't grasping efficiency

I'll happily try to understand an explanation. Maths was never a strong
point:-(

I assume boiler efficiency is non linear. Given that a fixed amount of
energy is required over a 24 hour period, and that boiler losses only
occur during firing, my uncertainty is whether a shorter firing period,
but at reduced efficiency, would use less gas overall.

This seems fundamental to matching boiler and set up to the expected
load.

Many seem to call something efficient if it simply works OK. And in that
respect an ancient boiler could be just as good as the best modern one.

True efficiency (for most) would be getting the same results for the
lowest running costs.

Efficiency is a ratio (usually %) of useful energy output divided by energy input.